Radio apparatus



A ril 18,1933. H. A. ANDERSON RADIO APPARATUS Filed March 10, 1930 INVENTO fibmerA.Ander.son,

BY M ATTORNEY a :w I w N WITNESSES Patented Apr. 18, 1933 UNITED STATES HOMER A. ANDERSON,

or BROOKLYN, NEW YORK RADIO APPARATUS Application filed This invention appertains to improvements in radio apparatus generally, and has for its main object to provide a receiving circuit characterized by extreme sensitiveness in reception of each assigned frequency in the present broadcast band of frequencies, maximum selectivity of the different assigned broadcast frequencies, substantially full tonal reproduction an maximum elimination of interference.

Another object of the invention is to provide a increase in t e received broadcast signal strength in the primary or antenna circuit of the improved hook-up, whereby the efficiency of both the radio and audio frequency amplifying net-works is correspondingly increased.

Still another object of the invention resides in the provision of a means to so sharpen the received broadcast signal of increase strength at the radio frequencyside of the hook-up that the extreme selectivity and perfect tonal reproduction as aforesai is obtained.

A further object of the invention has to do with the tuning of the received broadcast signal to a point of substantially perfect elimination of interference of all kinds immediately upon the increasing of its natura or normal strength and as it is passed in and through the radio frequency amplifying network.

A still further object of the invention l es in the combining of the grid and plate circuits of the radio frequency amplifying network into a substantially single circuit which functions as a by-pass or filter to interference frequencies, such as those produce y transmitting stations whose signals it is desired to receive and by strays, static and the like, while the frequency passes directly to side of the said net-work.

Another object of the invention resides in the by-pass circuit aforesaid being arrange to filter the interfering frequencies past the radio receiving amplifier and to ground before detection and, in the case of several stages of such amplification being employed,

selected broadcast signa the functioning 1 tical embodimentof' the invention is March 10, 1930. Serial No. 434,649.

circuit will be grounded immediately following each stage thereof.

A further object of the invention is to provide adjustable condensers between the grid and plate electrodes of each of the tubes of the radio frequency amplifying net-work and of the detector located between thesaid net-work and the audio frequency amplifying net-work, whereby to effect the desired sharpness in tuning of the hookup as a whole, as well as to provide the by-pass circuit aforesaid for the elimination of the interference frequencies to ground.

Another object of the invention is presented in the provision of adjustable condensers connected across the primary and secondary windings of the transformers employed in the radio frequency amplifying net-work, which function to prevent the transference through the transformers to local and static interference.

Still another object of the invention has to do with the provision of adjustable resist-' ance, such as Bradleystats or the like, togeth- 7 er with fixed condensers, in the grid circuits 5 of each of the tubes employed in the audio frequency amplifying net-work, in order that such interfering frequencies, particularly those of a popping and crackling nature will be separated from the amplified and detected broadcast signal and by-passed to ground before reaching the output side of the netthe bypass or filter work.

With the foregoing and other equally important objects and advantages in view, the invention resides in the certain new and useful hook-up of radio instrumentalities as will be hereinafter more fully described, set forth in the appended claims and illustrated in the accompanying drawing.

Referring to the drawing, wherein a pracdepicted diagrammatically by way of example only, the primary circuit of the hook-up is constituted in an antenna 1, which is connecte to a ground 2 through he primary winding 3 of an induct've coupling 3,,the secondary winding 3 of the latter being arranged in the input side of the, first stage of a ra io frequency amplifying net-work An adjustable condenser 4 is connected between the the grid 9 of the first radio frequency ampliantenna 1, at a point immediately above the fying tube RFl, from whence a selected primary winding 3, and the lower side of broadcast signal will pass successively from the secondary winding 3 of the inductive stage to stage of radio frequency amplificacoupling3 and from thence direct toaground tion, by way of-the tubes RFl, RFQ and 7 5 which has the effect of increasing the RF3 and the associated transformers RTl, strength of the broadcast signal absorbed by RTQ and RT8 to the detector tube D, while the antenna 1. all interfering frequencies will be separated By this arrangement of the primary windout therefrom and passed to ground as will ing 3, between the antenna and ground, the be nowfully explained. same functions somewhat as a choke coil to This separating out of interfering frepass low interfering frequencies to ground, quencies from the selected broadcast signal as will be hereinafter fully explained; frequency and the subsequent elimination of In addition to the tuned effect given to the the same by being shunted around the sevprimary or antenna circuit by the condenser eral radio frequency amplifying tubes RFI, 4:, the same is to be selectively tuned by means RFEZ and REE the detector tube D and the of a variable capacitance 6 which is shunted radio frequencytransformers RTl, RTQand across the terminals of the secondary wind- UB3 to the grounds 8 is effectively acconr ing- 3" of the inductive coupling 3. plished by the inter osing of adjustable'con In the present instance of the invention, densers 0, c 0 anc 0 respectively, between three stages each of radio and audio frethe grid 9 and the plate 39 of each of the quencyamplification are employed, with a radio frequency amplifier tubes and bridgdetector circuit interposed between the outing the upper terminals of the associated put side of the last stage of the former and transformers with similar condensers C, C the first stage of the latter and the tubes of and C I p each amplifying net-work are connected in The tuning of the second and third stages cascade by suitable couplings. As shown, the of radio frequency amplification and the deradio frequency amplifying net-work intector circuit is effected by associated varicluding the tubes R-Fl, RF 2 and RF3, which able condensers VC V0 and V0 respecare preferably all of the -26 type; the detively, which areconnected between the grid tector circuit a tube D of the -27 type; circuits of the radio frequency tubes RFQ, and the audio frequency network the tubes RF3 and the-detector tube D and the lead AFl, AF 2 and AFS of which AF 1 and A1 2 9 from the negative side B current source. are of the -26 type and AF 3 of the 71A In order to sharpen the tuning of the detectype. tor circuit, an adjustable condenser 10 is con- 1 The radio frequency amplifier tubes RF 1, nected at that side of the variable condenser RF 2 and RF3 are coupled in cascade by trans- VG, which is connected to the grid circuit formers RTl and RT2 and RT3 and the deof the detector tubeD, and in shunt about tector tube D and the audio frequency amthe same to ground 10.

' plifier tubes AFl and AF2 and AF3 by the The filaments f of all of the several radio 1 transformers ATl, AT2, and AT8. The upand audio frequency amplifying tubes, as per-terminalsof each of the primary windwell as that of the detector tubellare conings P, of each of theradio and audio frenected to the positive and negative leads l1 quency transformers are directly connected and 12' of the A current source, substanto the plate or anode of the tube immediately tially as shown.

preceding the same, while the similar ter- The elimination of interferences from the minals of each secondary winding Sis directselected and amplified broadcast signal frely connected to the grid 9 of the amplifier quency is continued after detection anddurimmediately ad acent thereto, except that a ing its transference to and through the audio combined grid condenser GC and grid leak amplifying tubes AFLAFQ and AF3 and the L unit is interposed between the secondary associated transformers ATl, AT2 and ATS S of the last stage radio frequency transby the lower sides of the secondary windformer RT3 and the grid 9 of the detector ings S of the latter being connected to the tube D. grounds 8. Here, the interference frequen- The lower terminals of the primary windcy by-pass circuit around the three stages ings P of both sets of transformers RTl, of radio frequency amplification and the de- RTQ and RT3 and ATI, AT2 and AT3 are tector tube .D terminates with the connection I connected to a common lead 7 from the posiof the grid circuit of the latter tube to the tive side of the B current source, while the upper side of the variable condensers VC similar terminals of the secondary windings and the shunted adjustable condenser 10, S are all connected to grounds 8. The output which have the lower sides of the same consideof the primary or antenna circuit, i. e., nected to the ground,-the condenser VC to t eupper terminals of the secondary winding the ground 9 of the negative B current 3", of the inductive coupling 3and the varilead 9 and the condenser 10 to its associated ab e capacitance 6, is connected directly to groundlO. s V

- l of the final audio frequency RF?) and of From this point on through the several stages of audio frequency amplification the interference will be, in the main, largely of the local and static type, generally evident by so-called popping an crackling noises or sounds, and this is effectively eliminate by way of the grounds 8, to which the lower sides of the secondary winding S of the audio frequency transformers ATl, ATQ and AT3 are connected. This elimination of the interferences is aid-ed by the connecting of variable resistances VR1, V132 and VH8 in series with companion adjustable condensers 13, 1-; and 15, and between the grid circuits of the tubes AFl, AFZ and AF3 and the ground 9 of the negative B current lead 9.

The plate 29 of the last audio frequency amplifying tube AF3 is connected by a lead 16 to one terminal of the primary winding transformer AT which has its other terminal connected, as at 17, to the positive B current lead 7. The secondary winding S of the transformer AT i outputs the purified selected and amplified broadcast signal frequency to a loud speaker or the like (not shown).

In order to finally clarify the selected and amplied broadcast signal frequency, and prior to its reception at the loud speaker, a variable resistance Vite, arranged in series with an adjustable condenser 18 is shunted across the output leads from the secondary winding S of the transformer 1 T4.

The V27 type of detector tube D is preferyed because of the fact that it functions with less noticeable hum in the output than do all other types of tubes suitable for use as detectors.

In placing the receiver in use, after the completion of the hook-up, the condenser 4 will be adjustable to initially tune the primary or antenna circuit to a given broadcast signal frequency. Thus, by adjusting this condenser to the capacity of the lowest frequency division of the present broadcasting band of frequencies, the several higher divisions throughout the band range will be capable of pick up and subsequent separation upon the adjustment of the other capacitance controls of the hook-up. After the adjustment of the primary or antenna circuit, the adjustable condensers 0, 0 c and 0 bridging the grid 9 and plate p circuits of the radio frequency amplifying tubes RFl, RF2 and the detector tube D will be adjusted successively to points where any incoming interferences will be reduced to an absolute minimum if not totally eliminated. Similarly, the adjustable condensers C, and C bridging the upper of the terminals of the primary and secondary windings and S of the radio frequency transformers RT1, RTQ, and RT3 will be adjusted to further the interference elimination.

Likewise the resistors or Bradleystats d ly,

V31, V112 andV3 together with their companion condensers 13, 14: and 15, Willbe ad'- justed to similarly reduce the interferences, tending to pass to the output, to absolute minimum effect or total elimination. Finalhe resistor or Bradleystat VR l and its companion condenser justed to a point of absorption of any interferences which might be picked up in the secondary winding of the last audio frequency transformer AT l.

Thus, with the condensers connected in line throughout the radio amplifying and detector network, low interfering frequencies will be blocked out, while the higher signal frequencies will readily pass along this route. to the audio amplifying network. Similarly, the low frequencies will be readily gotten rid of by passing to ground, after each stage 0 radio amplification and the stage of detection, by way of the secondary windings S of the transformers RT RT and RT and AT, which windings also act as choke coils to block out the higher frequencies.

Having thus filtered out interferences from the primary circuit and those getting by the successive stages of radio amplification and the detector stage, of frequencies 0 lower value, at', least as compared to that of the amplified signal frequency, will be readily passe to groun through the resistors or Bradleystats following the detector stage and each of the severalstages of audio amplification, while the punfied signal current of high frequency will e blocked out thereby and will be passed directly to the output side of the audio amplifying network. 1

In the receiver shown, the condensers G and 0 (general designation) within the radio frequency range are of a sufiicient capacity, say .0005 microfarad, to let any amount 0 current through that will allow the receiver to perform with clearness in tonal reproduction and, at the same time, by-pass the undesired frequencies to be checked from passing through circuit. The condensers 13, 1e and 15,within the audio frequency range may be from one-half to one microfarad, with the Bradley stats VR VH and VR, in series therewith, adjusted to take out interferences, regardl how severe, to a minimum and Lin-noticeable degree. The condenser 18, in the output circuit, will preferably have a capacity of two microfarads. I

It is to be especially noted that the radio frequency transformers RT1, RT2 and RT3 are connected in the net-Work with A and B currents connected on the extreme or outside ends of the windings, while the grid and plate circuits are si e by side, in which arrangement, sharper tuning is obtained than would be the case with the usual reverse manner of hook-up of these transformers. 1

other interfering currents the tubes and amplified 1n the 18 will likewlse be ad- 7 instrumental'i'ties employed may be resorted mary to, without departing from the spirit of the invention-or its scope as claimed. a

1 claim 1. A tuned antenna circuit comprising an aerial, an inductive coupling having its priend of theaerial and the ground, a fixed oapacitance interposed between the input end of the aerial and the lower side of the secwinding of the inductive coupling function in shunted relation with respect to the said primary winding and a ground connection leading fromthe connected adjacent sides of said condenser and the said secondary winding.

2'. A tuned antenna circuit comprising an aerial, aninductive coupling having its priwind ing interposed between the input end of the aerial and the ground, an adjustably fixed capacitance interposedbetween the input end of the aerial and the lower side of the secondary winding of the inductive coupling'whereby to function in shunted relation with respect to the said primary Winding and aground connection leading from the connected adjacent sides of the said condenser and the said secondary winding.

3. In a radio receiver circuit including a radio frequency amplifying net-work, antenna circuit comprising an aerial, an inductive coupling having its primary winding interposedbetween theinput end of the aerial and the ground and the upper side of its secondary Winding connected to the grid circuit of the said amplifying network, a variable capacitance interposed between the grid'con nected' side of the secondary winding and the ground,-an adjustably fixed capacitance intere posed between the input end of the'aerial above the said primary winding and the lower side of the said secondary winding whereby nctionin shunted relation with respect to the said primary winding, and a connection between the latter connected sides of the adjustably fixed capacitance and the said sec ondary wind ing and the ground.

A radio receiving system including a radio frequency amp ifying network consisting of a plurality of inductively coupled stages, capacitative by-pass means coupled'between the input and output circuits of each stage and between the inductive couplings thereof, andm eans including a reactance coupling said by-pass means to ground.

5. A radio receiving system including a plurality of inductively coupled stagesof radio frequency amplification and a stage. of detection inductively coupled to the output side of stage of inductively the last of the said amplification stages, a dabetween the pling said by-pass means to ground at'the output side of the said detection stage.

radio receiving system including a coupled radio frequency amplification and a stage of detection inductively coupled to the ground.

7. A radio receiving system including a radio frequency amplifying network consisting of a plurality of inductively coupled stages, capacitative by-pass means coupled between t e input and output circuits of each stage and between the inductive couplings thereof, and a plurality of means each including a reactance coupling said by-pass means to ground.

8. A radio receiving system including a radio frequency ampli ing network consisting of a plurality of inductively coupled stages, capacitative bypass the input and output circuits of each stage and between the inductive couplings thereof, and a means including a reactance coupling each y-pass means to ground.

radio receiving system including a radio frequency amplifying network consist ing of a plurality of inductively stages and a stage coupled to the output side of the last amplification-stage, capacitative by-pass means cou pled between the input and output circuits of each amplifying stage and between the inductive couplings between the same and that ing a reactance coupling said by-pass means to ground.

I '10. A radio receiving system including radie and audio frequency amplifyingnetworks,

each consisting, of a plurality of inductively coupled stages, and a stage of detection inductively coupled l etween the said networks, capacitative by-pass means coupled between the: input and output circuits of each stage of the radio HOMER. A ANDERSON;

fret uenc am lif in network and 

